Exercise machines for simulating walking or running are known and used for directing the movement of a user's legs and feet in a variety of repetitive paths of travel. The user typically performs an exercise using such a walking or running machine for an extended period of time such as one to 30 minutes without interruption and without stopping to perform a different exercise using a different machine such as a user might perform in a circuit protocol of exercise. The machines typically include an electrically powered mechanism that the user can activate to adjust some aspect of the machine such as degree of resistance. Running or walking simulation machines commonly referred to as elliptical path machines have been designed to pivot the foot pedals on which the user's feet reside guiding the pedals and the user's feet to travel in an elliptical or arcuate path. The degree of resistance to performance of the exercise in such prior art machines typically varies linearly with the degree of force or speed exerted by the user to a moving mechanical component of the apparatus. The path of travel of the foot pedal in such prior machines is not adjustable other than to change the shape of the ellipse. The foot travels along a different path from back to front than from front to back in such elliptical machines.